Method for determining an analyte in a water sample by means of a mobile water analysis arrangement

ABSTRACT

A basic unit for a mobile water analyzing system includes a photometer comprising a light source configured to generate a measurement beam and a light detector configured to receive the measurement beam, a test element receptacle configured to allow a test element to be inserted therein, and a photometric measuring track arranged between the light source and the light detector. The measurement beam is coincident with the photometric measuring track during a photometric measurement, and not in a cross direction thereto.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/122,561, filed on May 10, 2011. U.S. application Ser. No. 13/122,561is a U.S. National Phase application under 35 U.S.C. § 371 ofInternational Application No. PCT/EP2009/062535, filed on Sep. 28, 2009and which claims benefit to German Patent Application No. 10 2008 050092.5, filed on Oct. 6, 2008. The International Application waspublished in German on Apr. 15, 2010 as WO 2010/040657 A1 under PCTArticle 21(2).

FIELD

The present invention provides a method for determining an analyte in awater-sample with a mobile water-analyzing system. The present inventionalso provides a mobile water-analyzing system for determining theaforementioned method as well as a basic unit and a test-element of therespective mobile water-analyzing system. “Mobile” means that thewater-analyzing system of the present invention is not stationary as acontinuously working process analyzing-device.

BACKGROUND

The prior art in the field of mobile water-analysis is currentlyrepresented by so-called photometric cuvette tests as described in DE 4109 118 A1. The use of these tests is performed manually. First, awater-sample is taken by a pipette and given into the cuvette. Fordetermining the self-absorption of the water-sample, i.e., the so-calledbackground signal, the water-sample is inserted into the photometer andis measured. A reagent is then added to the water-sample in the cuvette.The cuvette is closed and shaked to mix the water-sample with thekey-reagent. It is subsequently inserted into a photometer and measured.

The handling of such a cuvette test is inconvenient and extremelysusceptible to errors. The used reagent can be dangerous for health andthe environment, so that the used cuvette tests must be disposed in anappropriate way. The inconvenient handling makes the cuvette tests onlyapplicable for use in a laboratory. Such water-sample analyzation,including the determination of the self-absorption of the water-sample,can be performed automatically in a non-mobile water-analyzing system.

SUMMARY

An aspect of the present invention is to provide a method or a devicefor determining an analyte in a water-sample including the determinationof the self-absorption of the water-sample with a mobile water-analyzingsystem with improved handling.

In an embodiment, the present invention provides a basic unit for amobile water analyzing system which includes a photometer comprising alight source configured to generate a measurement beam and a lightdetector configured to receive the measurement beam, a test elementreceptacle configured to allow a test element to be inserted therein,and a photometric measuring track arranged between the light source andthe light detector. The measurement beam is coincident with thephotometric measuring track during a photometric measurement, and not ina cross direction thereto. The present invention also provides a testelement for a mobile water analysis system which includes a microfluidicsample line. The microfluidic sample line comprises an inlet openingdisposed at a first end, a pump port disposed at a second end of themicrofluidic sample line, an inlet section disposed between the inletopening and the pump port, a measuring section comprising at least onewindow arranged at an end of the measuring section, a first reagentsection disposed either between the inlet opening and the measuringsection or between the measuring section and the pump port, and areagent disposed in the first reagent section of the microfluidic sampleline. The inlet opening is configured to receive a water sample. Themeasuring section is arranged between the inlet section and the pumpport and is coincident with a sample pathway. The measuring sectionforms a photometric measuring track for a photometer so that ameasurement beam of the photometer and the photometric measuring trackare aligned during a photometric measurement so that the photometricmeasurement occurs along a length of each of the photometric measuringtrack and the measuring section, and not in a cross direction thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basisof embodiments and of the drawings in which:

FIG. 1 shows a schematic drawing of a mobile water-analyzing systemcomprising a basic unit and a test-element, to determine the methodaccording to the present invention;

FIG. 2 shows the test-element of the water-analyzing system of FIG. 1;

FIG. 3 shows an embodiment of a mobile water-analyzing system includinga removable cartridge with several test-elements, to determine themethod according to the present invention;

FIG. 4 shows the removable cartridge of FIG. 3;

FIG. 5 shows an embodiment of an electrochemical-optical test-element ina front view;

FIG. 6 shows a rear view of the test-element of FIG. 5;

FIG. 7 shows a side view of an embodiment of a test-element with a pumpmembrane, which is controlled via a pump actuator from the basic unit.

DETAILED DESCRIPTION

The method for determining an analyte in a water-sample refers to amobile water-analyzing system with a mobile basic unit and a removabledisposable test-element which is inserted or is insertable,respectively, into the basic unit for determining the analyte.

The test-element is a complex prefabricated part, whereby thetest-element is provided with a sample-line with an inlet opening whichis positioned at the distal end of the test-element. A measuring sectionis provided in line of the sample-line, the sample-line being providedwith a measuring track for an analyzer which is provided at the basicunit. All other parts of the analyzer are positioned in the basic unitand not in the test-element. The basic unit is further provided with areceptacle for holding the inserted test-element.

In the further course of the sample-line, a reagent section is provided,for example, in a section after the measuring section as seen from theinlet opening. The reagent section is provided with a reagent which canbe, for example, a key-reagent, an auxiliary-reagent or anauxiliary-agent. A key-reagent reacts with the analyte of thewater-sample by changing the color of the analyte, or the key-reagentreacts in such a way that an electrochemical analysis is possible. Anauxiliary-reagent also reacts with the water-sample, but not with theaim of a quantitative determination of the analyte in the water-sample,but rather with another aim. An auxiliary-agent does not reactchemically with the water-sample but influences the water-sample.

According to the present invention, the inserting of the test-elementinto the test-element receptacle of the basic unit is first provided.The inserting of the test-element can be performed manually orautomatically. The inlet opening of the test-element is then immersedmanually or automatically into the water to be analyzed and a definedportion or a defined volume, respectively, of the water-sample issegregated by transporting the water-sample forward so that thewater-sample is transported from the inlet opening to the measuringsection.

The creation of a defined portion of the water-sample can be realizedautomatically or semi-automatically: The insertion of the test-elementinto the test-element receptacle of the basic unit activates the basicunit for an analyte determination. In a next step, the inlet opening ofthe test-element is immersed manually or automatically into thewater-reservoir to be analyzed. After the immersion of the inlet openinginto the water-reservoir, the pump actuator is activated, whereby theimmersion can be detected, for instance, through a small pressureimpulse in the sample-line. The activating of the pump actuator can alsobe performed manually. By activation of the pump actuator, awater-sample is pumped actively through the inlet opening toward themeasuring section.

A defined volume of the water-sample is sucked and is segregated as asample-column, whereby the sample column at both ends is limited by air.By limiting the sample-column to a defined volume, a defined ratiobetween the water-sample and the key-reagent is provided.

The limitation of the water-sample portion to a defined portion can berealized by giving the customer a signal after the pump actuator hasstopped after a defined volume of the water-sample has been sucked sothat the customer obtains the information that the sampling is finishedand that the inlet opening can be taken out of the water to be analyzed.The segregation of the water-sample can also be made automatically byusing an appropriate valve which conducts air into the sample-line afterthe defined water-sample volume is sucked.

“Pumping forward” means a transporting in the sample-line upstream fromthe inlet opening. The forward pumping can be performed in any knownway, for example, by a pump in the basic unit, whereby the pump isconnected with the sample-line, or by a relative large pump volume whichis formed by a pump-membrane at the disposable test-element, whereby thepump-membrane is controlled via a pump actuator of the basic unit, forexample, by a push rod.

In the measuring section, a first analysis of the water-sample isperformed with the analyzer, for example, a sample background signal isdetermined. The first analysis can also basically be a quantitativedetermination of an analyte in the water-sample when a key-reagent ispositioned in the sample-line between the inlet opening and themeasuring section.

The analyzer can be an electrochemical analyzer which determines anelectrical parameter of the water-sample. Alternatively or additionally,the analyzer can be a photometer with a light source and a lightdetector.

As soon as the first analysis is finished, the water-sample istransported forward from the measuring section to the first reagentsection. The water-sample is mixed in the first reagent section with thefirst reagent. The first reagent can be a key-reagent, for example, areagent which colors the analyte of the water-sample. The first reagentcan alternatively be an auxiliary-reagent or an auxiliary-agent ofanother nature, for example, if a key-reagent is positioned between theinlet opening and the measuring section.

The first reagent can, for example, be a key-reagent which, for example,reacts with the analyte of the water-sample, whereby the reactionchanges the optical or the electrochemical properties of thewater-sample. Referring to the example of a photometrical analyzer, theabsorption spectra of the water-sample changes particularly at definedspectra lines or defined spectra areas, respectively. The first reagentcan also be an auxiliary-reagent which is not a detection-reagent oranother auxiliary-agent.

The prepared and homogenized water-sample, whereby the mixing of thewater-sample is performed, for example, by repeatedly pumping back andforth, can be transported backward from the first reagent-section to themeasuring section, whereby the water-sample can be analyzed a secondtime by the analyzer electrically and/or optically. The result of thesecond analysis can, for example, be a gross-value. For example, thebackground signal of the sample of the first analysis can be subtractedfrom the gross-value and lead to a net value of the analyte in thewater-sample. The net-value can be displayed and/or saved. As soon asthe net-value is displayed, the disposable test-element can be removedmanually or automatically.

All steps which are relevant for the quality of the measurement resultsof the water analysis, such as the analysis, for example, determiningthe background signal of the sample, the dosage of the first reagent,for example, the mixing of the first reagent with the water-sample, thewaiting for the reaction time etc., can be performed semi-automaticallyor fully-automatically, respectively, and air-tight. Errors and hazardsresulting from inaccurate handling can therefore be almost totallyexcluded.

In an embodiment, the present invention provides a method for adisposable test-element, whereby the test-element is provided with asample-line and a measuring section, whereby the water-sample is pumpedforward after a first analysis of the water-sample in the measuringsection to a first reagent-section in order to be mixed with the reagentand pumped backward to the measuring section to be analyzed again. Thewater-sample can be mixed with the key-reagent before the first analysisor can be transported free of reagent to the measuring section toperform a first analysis, for example, to determine a background signalof the sample. The positioning of a reagent in a first reagent sectionwhich is behind the measuring section allows numerous options to performone or several analysis, respectively, and to improve further propertiesof the disposable test-element.

According to an embodiment of the method of the present invention, thesample-line can, for example, be provided with a second reagent sectionwith a second reagent which can, for example, be an auxiliary-agent,whereby the second reagent section can be positioned beyond the firstreagent section. The following method steps are performed subsequentlyto the water-sample analysis:

transporting the analyzed water-sample forward to the second reagentsection.

The water-sample reacts in the second reagent-section with the secondreagent, for example, with an auxiliary-agent. A second reagent behindand separated from the first reagent or first reagent-section,respectively, as seen from the measuring section, allows the realizationof numerous additional functions. For example, the second reagent can bean auxiliary-agent which is formed as a gelling agent and/or color agentso that the water-sample is gelatinized and/or colored after theanalysis of the water-sample. Gelatinizing causes a fixation of thewater-sample in the sample-line so that leakage is avoided. Changing thecolor of the water-sample shows the customer and/or the analyzer whichdetects the change of the optical properties that the disposabletest-element is already used.

The water-sample can, for example, be transported backwards from thesecond reagent section to measuring section, so that the water-samplecan be analyzed a third time by the analyzer. A third reagent sectioncan be positioned behind the second reagent section, for example, with asecond auxiliary-agent, whereby the following method steps are performedsubsequently to the third analyzing of the water-sample:

transporting the water-sample forward to the third reagent section;

transporting the water-sample backward from the third reagent section tothe measuring section; and

performing a fourth analyzing of the water-sample with the analyzer.

Both auxiliary-agents in both auxiliary-agent sections, for example, thesecond and the third reagent section, can, for example, beanalyte-standards with different respective quantities orconcentrations. The described method allows the performance of astandard-addition so that a calibration can be performed at eachmeasuring sequence. The actual and exact concentration of the analyte inthe water-sample can be determined by calculating the regression of theresult of the key-reagent analysis of the water-sample.

It is also possible to provide more than two reagent sections withrespective auxiliary-agents or analyte-standards, respectively, so as toincrease the accuracy of the calibration, for example, with non-linearcharacteristics.

The test-element can physically have a size of a flat match stick sothat the sample-line can have a corresponding small cross-section, whichis in a range between 0.01 mm² and some square millimeters. Thephotometrical section or the measuring track, respectively, should be aslong as possible, for example, in the range of some millimeters to somecentimeters. The volume of the water-sample in the photometrical sectionis therefore in the range of one to about one hundred cubic millimeters.According to the dimensions, the amount of the reagent is small so thatthe potential danger for health and the environment is low as well. Theneed for an appropriate disposure can therefore be avoided so that aconsiderable effort for the appropriate disposure or recycling to thedistributor or producer, respectively, can be avoided.

All steps which are relevant for the quality of the measurement resultsof the water analysis, such as the dosage of the analyte, the mixing ofthe analyte with the water-sample and the waiting for the reaction timeetc., are performed semi-automatically or fully-automatically,respectively, and air-tight. Errors and hazards resulting frominaccurate handling can therefore be almost completely excluded.

The analyzer can, for example, be a photometer with a light source forgenerating a measurement beam and a light detector for receiving themeasurement beam, whereby the measuring section which is passed throughby the beam can be formed by a photometer section. The photometer can,for example, be provided as a transmission-photometer. Atransmission-photometer has, compared with a reflection-photometer, abetter information signal. The transmission-photometer allows for a moreprecise quantitative determination of an analyte at a relative shortmeasuring track. The measuring section can be provided with at least onephotometrical-window for the inlet and the outlet of the measuring beam.With the photometrical method, different ions, for example, chlorine,phosphate and ammonium, can be measured.

The analyzer can alternatively be an electrochemical analyzer whichdetermines an electrical parameter in the measuring section. Themeasuring section can be provided with at least one electrode or sensorarea, respectively, which is connected through electric lines withcontacts or contact areas of the test-element, respectively. Thecontacts of the test-element can be connected with the basic unitthrough contacts or through contact areas, respectively, and thereforewith the analyzer of the basic unit. The electrode or sensor area,respectively, has an area of some square micrometers to somemillimeters. Different parameters, for example, conductivity, redoxpotential, pH-value and oxygen content oxygen, can be measured with theelectrochemical method.

The basic unit can alternatively be provided with a photometrical, anoptical or an electrochemical analyzer, respectively, so thatphotometrical, optical and also electrochemical test-elements canalternatively be used at the basic unit.

The test-element can be provided with a positioning element which canprovide an exact positioning of the test-element in the basic unit. Themeasuring section of the test-element must be exactly in line with thephotometer of the basic unit to provide a photometrical measurementwithout errors. The test-element can therefore be provided with at leastone separate positioning element, which provides the positioning inaddition to the lateral surface of the test-element in the basic unit.For example, the test-element can comprise a groove, a cavity or anopening in which a respective snap element of the basic unit snaps in soas to position and fix the test-element into the basic unit.

The reagent or the reagents, respectively, can, for example, be providedin a dry state in the sample-line. It is also possible to arrangenumerous different key-reagents or detection-reagents in series in thesample-line behind the measuring section. Once the water-sample arrivesat the respective key-reagent, the reagent is dissolved in thewater-sample and reacts with the analyte, for example, by changing thecolor.

The test-element can, for example, be provided with a pump-membranewhich can be controlled via a pump actuator of the basic unit, wherebythe pump actuator can be provided, for example, with an electromotiverod. The flexible pump-membrane can be positioned at the opposite end asseen from the inlet opening on the sample-line and seals the pumpopening of the sample-line air-tight so that air is pushed and thewater-sample is transported in the sample-line by a deformation of thepump-membrane. Pushing or deformation, respectively, of thepump-membrane causes a transporting of the fluid backward, whilereleasing of the pump-membrane causes a transporting of the fluidforward in the sample-line. The releasing of the membrane can beperformed by the resilience of the membrane or by pulling the membranewith the pump actuator. Both the pump-membrane and the pump actuator canform a membrane-pump, whereby the test-element can be provided with thepump-membrane. The electromotive pump actuator or the rod, respectively,can be positioned in the basic unit.

The test-element can alternatively be provided with a pump-opening inthe sample-line. The pump-opening can be positioned at the opposite endas seen from the inlet opening on the sample-line. The basic unit can beprovided with sample pump which is connected with the insertedtest-element as soon as the test-element is inserted in the basic unit.

In an embodiment of the present invention, an absorption body can, forexample, be arranged between the measuring section and the pump opening.The absorption body serves to absorb the water-sample after thewater-sample has been finally analyzed and is transported forward to theabsorption body. The water-sample can thereby be immobilized and aleakage of the water-sample avoided. For example, the absorption bodycan be a fleece body, a clay body like bentonite or can be a so calledsuper-absorber. The body can additionally comprise a neutralizingreagent.

In an embodiment of the present invention, the sample-line can, forexample, be provided with a sample filter which filters the water-samplewhich is sucked through the inlet opening of the test-element. Thefiltration can be performed before the water-sample is transported tothe measuring section to be analyzed, for example, analyzedphotometrically. The sample filter can be made of mineral wool.

According to an embodiment of the present invention, the sample-linecan, for example, be provided with a dose capillary which can bearranged between the inlet opening and the measuring section. The dosecapillary can, for example, be arranged adjacent to the inlet opening.By using a dose capillary, the water-sample can be sucked, basically bythe capillary force, into the test element so that a definedwater-sample volume can be segregated. The water-sample can thereafterbe pumped repeatedly forth and back inside the sample-channel by usingthe pump actuator.

The test-element can be provided with a drying agent to protect thekey-reagent against humidity. For example, the drying agent can beseparated in the sample-line by using a hydrophobic stopper capillary,whereby the humidity can flow through the stopper capillary to thedrying agent.

The inlet opening and/or the pump opening can be sealed with ahumidity-tight transport-seal which can be opened manually orautomatically by inserting the test-element into the basic unit, forexample, by piercing. The single test-element can alternatively oradditionally be sealed in a humidity-tight package.

FIGS. 1 and 3 schematically show a mobile water-analyzing system 10, 10′for a quantitative determination of an analyte in a water-sample. Withthe described embodiment of a photometrical analyzing system 10, 10′,chlorine, phosphate or ammonium can be determined. Alternatively oradditionally, the analyzing system can be provided as an electrochemicalanalyzing system with an electrical analyzer.

The analyzing system of FIG. 1 comprises a basic unit 14 and a removabledisposable test-element 16 which is presently inserted into the basicunit 14.

The test-element 16 is provided with a test-element body 18 made ofplastic. The test-element body 18 is provided with a sample-line 20which is formed as a groove. The side of the groove opening of thetest-element body 18 is closed with a transparent plastic film oraluminum cover, respectively (not shown).

The sample-line 20 is provided with an inlet opening 22 which ispositioned at the distal end, referring to the basic unit 14, andthrough which a water-sample is sucked from a water-reservoir 12.Adjacent to and, in the flow direction, behind the inlet opening 22. isa meander-like mix section 26 of the sample-line 20 in which akey-reagent, an auxiliary-reagent or an auxiliary-agent and the suckedwater-sample are homogeneously mixed.

A measuring section 28 is arranged adjacent to the mix section 26 inwhich a quantitative determination can be performed. The presentmeasuring section 28 is a photometrical section, whereby the measuringsection 28 forms a measuring track for the respective photometricalanalyzer 30 of the basic unit 14. Both sides of the photometer section28 comprise a clear-transparent photometrical window 44, 46 as shown inFIG. 2. The test-element body 18 can be completely made out of a cleartransparent plastic which allows the measuring beam 35 to pass throughthe measuring section 28.

Proximal to the measuring section 28, i.e., behind the measuring section28 as seen from the inlet opening 22, is a reagent section 23 with a dryreagent 24 which is a key-reagent. At the sample-line end opposite tothe inlet opening 22, i.e., behind the first reagent section 23, a pumpopening 40 as a pump element is provided which is connected with a pumpactuator of the sample pump of the basic unit when the test-element isinserted into the basic unit 14.

The basic unit 14 is provided with an analyzer 30 which is atransmission photometer with two light sources 32, 33 and a lightdetector 34. The light-sources 32, 33 emit light of differentwavelengths and the light detector detects both wavelengths.

The test-element 16 is provided with a positioning element 48 which isrealized as an opening. The positioning element 48 cooperates with arespective snap element of the basic unit 16 so that the test-element 16is fixed reproducibly and exactly. This provides that the measuring beam35 generated by the light source 32, 33 is exactly in line with thephotometrical measuring section 28. The test-element receptacle of thebasic unit 14 is formed as a slot 15 in which the test-element 16 fitswithout any clearance.

FIG. 3 shows a second embodiment of a mobile water-analyzing system 10′including a removable cartridge 60 which is formed as a drum with 15drum chambers 62, whereby each drum chamber 62 carries a test-element16. The plastic drum body 64 is sealed axially with a circular sealingfoil 66 so that the chambers 62 are sealed gas-tight and fluid-tight.

As shown in FIG. 3, the removable cartridge 60 is inserted into arespective cartridge slot of the basic unit 14′. The basic unit 14′ isprovided with a cartridge rotary actuator 67 and a test-element shifter70. The shifter 70 can shift a test-element 16 automatically from achamber 62 into the measuring position as shown in FIG. 3.

As soon as the measurement is finished, the shifter 70 moves thetest-element 16 out of the measuring position and ejects it out of thebasic unit 14′. In a next step, the shifter 70 is completely removedfrom the cartridge 60; subsequently the rotary actuator 67 turns thecartridge 60 by one chamber angle so that the next chamber 62 with thetest-element 16 is in line with the shifter 70. As soon as a measurementrequest is signalized by the customer, the shifter 70 moves thetest-element 16 from the chamber 62 into the measuring position so thatthe measurement can start.

FIG. 5 and FIG. 6 show the front view and the rear view of embodimentsof a test-element 80. The test-element 80 is an electrochemical-opticaltest-element which is provided with an electrochemical-optical measuringsection 82 in the sample-line 84. The measuring section 82 is providedwith two electrodes 86, 88 positioned opposite to each other, theelectrodes being connected through electric lines 90, 92 with contacts94, 96. The contacts 94, 96 are arranged in line to respective contactsof the basic unit whereby the contacts are connected with theelectrochemical analyzer of the basic unit. The measuring section 82 isfurthermore provided with an optical measuring track for the photometer.

Behind the measuring section 82, as seen from the inlet opening 22, is afirst reagent section 23 with a first reagent 24 which is a key-reagent24. Behind the first reagent section 23 is a second reagent section 25with a second reagent 27 which is a first auxiliary-agent 27. Adjacentto the second reagent section 25 is a third reagent section 29 with athird reagent 31 which is a second auxiliary-agent 31. Bothauxiliary-agents 27, 31 are analyte-standards with different quantitiesor concentrations, respectively.

The backside of the test-element of FIG. 6 is provided with the pumpopening 40 as a pump element of the test-element 80. A circular sealelement 41 is provided surrounding the pump opening 40 to provide agas-tight connection between the sample-line 84 and a sample-pumprealized as a pump actuator 42.

FIG. 7 schematically shows a side view of a part of an embodiment of amobile water-analyzing system 10″. The water-analyzing system 10″ isprovided with a disposable test-element 116 which is provided with aconvex and vesicular pump membrane 118 above the pump opening 40. Thepump element, which is formed as a pump membrane, 118 has a pump volumewhich is higher than the total volume of the sample-line 84.

The basic unit 114 is provided with a pump actuator 120 with a motor 122whereby the pump actuator 120 controls a rod 124. The rod 124 pushes thepump membrane 118 of the inserted disposable test-element 116. Thewater-sample can be moved over the complete length of the sample-lineforward and backward by the rod 124 deforming the pump membrane 118.

To determine an analyte in a water-sample, a test-element 16 is firstinserted into the test-element receptacle of the basic unit 14. Thebasic unit 14 can, for example, be activated thereby. In a next step,the inlet opening 22 of the test-element is immersed manually into theanalyzing water-reservoir 12 so that the sample-pump 42 sucks awater-sample into the measuring section 28 of the sample-line 20. Theanalyzer 30 determines in a first analysis the background signal of thewater-sample in the measuring section.

As soon as the background signal determination is finished, thewater-sample is pumped forward from the measuring section 28 into thefirst reagent section 23. The water-sample meets the key-reagent as thefirst reagent 24 in the first reagent section 23 so that the key-reagentis mixed with the water-sample. The key-reagent reacts with the analytein the water-sample so that the optical properties of the water-samplechange.

By pumping backwards, the water-sample flows back from the first reagentsection 23 to the measuring section 28. The water-sample is analyzed asecond time photometrically by the analyzer 30. The result of the secondmeasurement is a gross-value. Subtracting the background from thegross-value leads to a net concentration of the analyte in thewater-sample.

With the test-element 80 of FIG. 5 and FIG. 6, an even more precisedetermination of the analyte in a water-sample can be realized by usingstandard addition. After the determination of the analyte in themeasuring section 82, the water-sample is again pumped forward to thesecond reagent section 23 which is provided with a second reagent 27.The second reagent 27 is a first auxiliary-agent which is ananalyte-standard. The water-sample is mixed with the second reagent 27in the second reagent section 25. The water-sample is then pumpedbackwards from the second reagent section 25 into the measuring section82, whereby the water-sample is analyzed a third time photometrically.The water-sample is again transported forward to the third reagentsection 29, whereby the water-sample is mixed with the third reagent 31which defines a second analyte standard and which is a secondauxiliary-reagent. Finally, the water-sample is again transportedbackwards from the third reagent section 29 to the measuring section 82,whereby the water-sample is measured a fourth time by the photometer.

Both photometrical analyte standard measurements lead to aconcentration-absorption characteristic line which allows an exactdetermination of the analyte concentration of the water-sample by usingthe net concentration value.

Reagents 24, 27, 31 can alternatively be auxiliary-reagents of anotherkind.

The auxiliary-reagent can also be a neutralization-reagent. After thewater-sample has been analyzed in the measuring section 28, thewater-sample is pumped to the auxiliary-reagent which reacts with thekey-reagent in such a manner that the key-reagent is neutralized so thatthe test-element can be disposed of, for example, in the householdtrash.

The auxiliary-reagent can also gelatinize and/or color the water-sampleafter the water-sample has been analyzed. A change of the color of thewater-sample shows the customer that the test-element has been used. Thechange of the color can also be detected by the analyzer. Gelatinizingcauses a fixation of the water-sample in the sample-line so that leakageis avoided.

The auxiliary-reagent can also be an activator which activates thekey-reagent. The auxiliary-agent and the key-reagent must be arranged inline. The auxiliary-reagent activates the key-reagent as soon askey-reagent is being mixed with the auxiliary-reagent in thewater-sample. The key-reagent as well as the auxiliary-reagent can bepositioned between measuring section 28 and pump opening 40 oralternatively between inlet opening 22 and measuring section 28.

The present invention is not limited to embodiments described herein;reference should be had to the appended claims.

What is claimed is:
 1. A test element for a mobile water analysissystem, the test element comprising: a microfluidic sample linecomprising: an inlet opening disposed at a first end, the inlet openingbeing configured to receive a water sample; a pump port disposed at asecond end of the microfluidic sample line; an inlet section disposedbetween the inlet opening and the pump port; a measuring sectioncomprising at least one window arranged at an end of the measuringsection, the measuring section being arranged between the inlet sectionand the pump port and being coincident with a sample pathway, themeasuring section forming a photometric measuring track for a photometerso that a measurement beam of the photometer and the photometricmeasuring track are aligned during a photometric measurement so that thephotometric measurement occurs along a length of each of the photometricmeasuring track and the measuring section, and not in a cross directionthereto; a first reagent section disposed either between the inletopening and the measuring section or between the measuring section andthe pump port; and a reagent disposed in the first reagent section ofthe microfluidic sample line, wherein, the measuring section is formedby a longitudinal section of the sample line which is arrangedperpendicular to a length of the test element and parallel to a widestwidth of the test element, and the length of the test element is alongest side of the test element.
 2. The test element for a mobile wateranalysis system as recited in claim 1, wherein the microfluidic sampleline further comprises: a second reagent section disposed between themeasuring section and the pump port; and a second reagent disposed inthe second reagent section.
 3. The test element for a mobile wateranalysis system as recited in claim 2, wherein the microfluidic sampleline further comprises: a third reagent section disposed between thesecond reagent section and the pump port; and a third reagent disposedin the third reagent section.
 4. The test element as recited in claim 1,further comprising a seal element configured to surround the pump port,the seal element being configured to provide a gas-tight connectionbetween the microfluidic sample-line and a sample pump of a basic unitwhen the test element is inserted in the basic unit.
 5. The test elementas recited in claim 1, further comprising a pump membrane arranged abovethe pump port, the pump membrane being configured to be pushed by a pumprod of a pump actuator of a basic unit when the test element is insertedin the basic unit so as to move the water sample through the testelement.
 6. The test element as recited in claim 1, further comprising apositioning element configured to cooperate with a snap element of thebasic unit when the test element is inserted in the basic unit so thatthe test element is reproducibly fixed in the basic unit when the testelement is inserted therein.
 7. The test element as recited in claim 1,wherein the test element is provided as an electrochemical-opticaltest-element comprising: a first electrode, a second electrode, and anelectrochemical-optical measuring section each of which is arranged inthe microfluidic sample-line; a first contact; a second contact; a firstcontact line configured to connect the first electrode with the firstcontact; and a second contact line configured to connect the secondelectrode with the second contact, wherein, the first electrode and thesecond electrode are arranged opposite to each other, the first contactis configured to contact a first contact of the basic unit when the testelement is inserted in the basic unit, and the second contact isconfigured to contact a second contact of the basic unit when the testelement is inserted in the basic unit.